Loop takers for sewing machines



April 23, 1968 R. E. JOHNSON LOOP TAKERS FOR SEWING MACHINES OriginalFiled March 12, 1965 4 Sheets-Sheet VE N TOR. Ralph E Johnson AT ORNEYWITNESS April 23, 1968 R. E. JOHNSON LOOP TAKERS FOR SEWING MACHINES 4Sheets-Sheet Original Filed March 12, 1965 R mm Y N M E R V 0 0 E h m FmF 2 Y mm P 5 bm y M 2 N L l 8 m w 2 n April 23, 1968 R. E. JOHNSON3,379,150

LOOP TAKERS FOR SEWING MACHINES Original Filed March 12, 1965 4Shets-Sheet 5 I NVENTOR.

Ralph E. Johnson BY w i i- WA WITNESS April 1968 R. E. JOHNSON 3,379,150

LOOP TAKERS FOR SEWING MACHINES Original Filed March 1 1965 I 4Sheets-Sheet 4 INVENTOR.

Ralph E Johnson WITNESS BY W 5W WT ORNEY United States Patent 3,379,150L001 TAKERS FOR SEWING MAEIHINES Ralph E. Johnson, Boonton, N.J.,assignor to The Singer glompany, New York, N.Y., a corporation of Newersey Original application Mar. 12, 1965, Ser. No. 439,420. Divided andthis application Apr. 12, 1967, Ser. No.

3 Claims. (Cl. 112-228) ABSTRACT OF THE DISCLOSURE Cross reference torelated application This application relates to a loop taker for alockstitch sewing machine and is a division of my copending UnitedStates patent application Ser. No. 439,420, filed Mar. 12, 1965.

Summary 0 the invention It is an object of this invention to provide anovel circularly moving loop taker for a lockstitch sewing machineincluding a rotary loop taker body carrying the thread engaging beak, abobbin case, and a stationary bobbin case retainer which provides thesole constraint for the bobbin case radially, angularly and axially ofthe loop taker body. This novel arrangement eliminates the necessity forthe conventional bearing raceway between the loop taker body and thebobbin case and provides instead simply planar bearing surfaces ofengagement therebetween. In addition to the advantage of cost reductionmade possible by the simplicity of the loop taker construction of thisinvention the problem of thread jamming in the bobbin case raceway isobviated.

Description of the drawings One embodiment of the invention will bedescribed by way of example only with reference to the accompanyingdrawings in which:

FIG. 1 is a side elevational view of a sewing machine embodying a looptaker of this invention;

FIG. 2 is a vertical cross-sectional view of that portion of the sewingmachine of FIG. 1 in the vicinity of the rotary hook taken through theaxis of the rotary hook and illustrating the disposition of the sewingthreads during work penetration by the needle;

FIG. 3 is a vertical cross-sectional view similar to that of FIG. 2 andillustrating the disposition of the sewing threads after being actedupon by the rotary hook;

FIG. 4 is a top plan view of the parts illustrated in FIGS. 2 and 3 withthe sewing threads illustrated in the positions illustrated in FIG. 3;

FIG. 5 is a top plan view of the rotary hook and the surrounding portionof the sewing machine bed but with the work support and the bobbin andbobbin case removed;

FIG. 6 is a top plan view of the bobbin case showing the threadoccupying the position illustrated in FIGS. 3 and 4 thereon andincluding fragments of the rotary hook;

FIG. 7 is a bottom plan view of the bobbin case showing the threadoccupying the position illustrated in FIGS. 3, 4, and 6.

FIG. 8 is a vertical cross-sectional view similar to FIG.

3,379,150 Patented Apr. 23, 1968 2 and illustrating the disposition ofthe sewing threads shortly after seizure of a needle thread loop by abeak on the loop taker;

FIG. 8A is a top plan view of the rotary hook, bobbin, bobbin case andfragments of the sewing machine elements associated therewith in aposition corresponding to that illustrated in FIG. 8;

FIG. 9 is a vertical cross-sectional view similar to FIG. 8 andillustrating the disposition of sewing threads as the needle thread loopis about to be cast off the rotary hook beak;

FIG. 9A is a top plan view of the rotary hook, bobbin, bobbin case andfragments of the sewing machine elements associated therewith in aposition corresponding to that illustrated in FIG. 9;

FIG. 10 is a vertical cross-sectional view similar to FIG. 8 andillustrating the disposition of sewing threads as withdrawal of theneedle thread loop from a stored position on the bobbin case isinitiated;

FIG. 10A is a top plan view of the rotary hook, bobbin, bobbin case andfragments of the sewing machine elements associated therewith in aposition corresponding to that illustrated in FIG. 10;

FIG. 11 is a perspective view of the top of the bobbin case; and

FIG. 12 is a perspective view of the bottom of the bobbin case.

Detailed description Referring to the drawings, the sewing machineincorporating a loop taker of this invention is assembled preferably onan integral frame indicated generally at 11 and including a horizontalbase plate 12 from which extends a vertical standard 13. Secured beneaththe base plate 12 as by a bracket 14 and screws 15 is an electric motor16 having a shaft 17 extending vertically upward through an aperture 18in the base plate.

A rotary hook indicated generally at 26 is secured as by a set screw 21to the shaft 17. The rotary hook 20, the specific details of which willbe described hereinbelow, is of generally cylindrical form and forprotection of a sewing machine operator, is preferably arranged to turnwith slight clearance within a bore 22 formed in a support pedestal 23fixed as by screws 24 on the base plate 12. A top cover plate 25 seatedin a shallow counterbore 26 in the pedestal 23 and secured to thepedestal by screws 27 and 28 spans the hook accommodating bore 22 andalso sustains a raised work supporting plate 29 formed with a needleaperture 30.

A bobbin case indicated generally at rests upon the rotary hook and isboth located axially of the hook as well as constrained against rotationwith the rotary hook by cooperative interengagement with the top coverplate 25 and with rotation restraining means on the pedestal 23 as willbe described with greater particularity hereinafter together with thedetails of construction of the bobbin case. A thread carrying bobbin 41is freely journalled in the bobbin case and held therein by a leafspring 42 secured by the top cover plate fastening screw 28, which leafspring also serves frictionally to resist turning movement of the bobbinso as to provide bobbin thread tension.

A shaft is journalled in the standard 13 and has secured to it a balancewheel pulley 51. An electric motor 52 is supported on a bracket 53secured on the standard 13 and includes a motor shaft 54 having a pulley55 fast thereon and drivingly connected as by a belt 56 to the balancewheel pulley 51. Turning movement of the shaft 50 serves to impart workpenetrating endwise reciprocatory movement to an eye pointed threadcarrying needle 57, to impart operative movements to a needle threadtake up mechanism indicated generally at 58, and to operate a workfeeding mechanism indicated generally at 59.

A bracket 60 secured by screws 61 to the standard sustains a spool pin62 and a conventional needle thread tension device 63. Theseconventional parts are illustrated in FIG. 1 in dot and dashed lines soas not to obscure the other mechanisms of the sewing machine. The pathof thread from a spool on the spool pin 62 proceeds to the tensiondevice 63, to the needle thread take up mechanism 58 and thence to theeye of the needle 57.

The details of construction of the rotary hook 20, bobbin case 40 andassociated mechanisms will now be described in detail.

The rotary hook is formed with a central hub 201 in which the set screw21 is located and a cylindrical outer wall 202 merging with an inturnedflange 203 at the top. The flange 203 is notched radially at intervalsas at 204 to form inwardly directed thread seizing beaks 205 on theflange 203. The flange 203 may be formed with one beak 205 or with aplurality of beaks, stitching being possible using the principles ofthis invention with any number of beaks. As will be explainedhereinafter with reference to the mode of operation of this invention,the number of beaks merely constitutes one factor which may influencethe maximum practical speed of needle reciprocation relatively to thespeed of rotation of the hook. In the preferred embodiment illustratedin the drawings, four hook beaks 205 are used and it is also preferablethat the diameter of the flange 203 be gradually increased from eachbeak 205 to the next succeeding notch 204.

The central hub 201 of the rotary hook is formed with a raised boss 206spaced inwardly of the outer wall 202 to define therebetween an annularrecess 207 accommodat ing penetration of the needle 57. A frusto-conicalupper extremity 208 is formed on the raised boss 206 which together witha circular recess 209 formed in the upper end of the raised boss definesa narrow annular land 210 facing upwardly and disposed at a levelbeneath that of the flange 203 in which the loop seizing beaks 205 areformed.

Referring to FIGS. 4 and 5, a crosspiece 212 is set into the top of thepedestal 23 and is secured by screws 213 so as to span a chord of therotary hook accommodating bore 22. Secured by screws 214 to thecrosspiece is a wire leaf spring 215 having a bowed free extremity 216projecting beyond the crosspiece. The top cover plate 25 of the pedestal23 is provided above the bore 22 with a generally rectangular aperture217 formed with a step 218 adjacent to the needle aperture in the worksupporting plate 29. The leaf spring extremity 216 and the step 218engage the bobbin case to restrain the bobbin case from rotation and tolocate the bobbin case relatively to the rotary hook.

The bobbin case 40 is formed with a planar bottom surface 221 from whichrises a cylindrical sidewall 222 enclosing a cylindrical upwardly openbobbin accommodat ing cavity 223 formed concentrically with acylindrical stud 224 terminating in an upstanding bearing boss 225 onwhich the bobbin is adapted to be journalled. Projecting radially fromthe cylindrical sidewall 222 of the bobbin case is a flange 226 which atits periphery rests on top of the rotary hook flange 203 as illustratedin FIGS. 2 and 3. The bobbin case flange 226 is parallel to and spacedfrom the bottom surface 221 of the bobbin case base so that the surface221. rests upon the annular land 210 of the raised boss 206 on therotary hook.

Above the projecting flange 226, the outer surface of the bobbin casesidewall 222 is tapered and frusto-conical in form so as to projectthrough the top cover plate aperture 217 and slightly above the level ofthe top cover plate 25.

The bobbin 41 is formed with top and bottom flanges 230 and 231respectively which are preferably formed integrally with a hub portion232 as illustrated in FIG. 2. The bottom flange 231 is formed with acounterbore 233 which loosely embraces the bobbin case stud 224 and thecounterbore 233 terminates in a bore 234 which snugly accommodates thebearing boss 225 on the bobbin case stud 224. The leaf spring 42 bearsagainst the top flange 230 of the bobbin and urges a dependingperipheral rim 235 on the bottom flange 231 of the bobbin against thebobbin accommodating cavity 223 of the bobbin case frictionally toresist turning of the bobbin, and in addition the spring 42 urges thebobbin case flange 226 against the rotary hook flange 203 and the bottomsurface 221 of the bobbin case against the annular land 210 on theraised boss 20.. of the rotary hook.

Referring to FIGS. 6, 7, l1 and 12, both the bobbin case sidewall 222and the projecting flange 226 are cut away along a chord as indicated at240 which chord faces the path of reciprocation of the needle 57 whenthe bobbin case is positioned on the rotary hook thus providing needleclearance. Preferably a bevel 241 is formed on the bobbin case base inthe vicinity of the cut away portion 240 from the level of the flange226 to the bottom surface 221 of the bobbin case. Above the level of theflange 226, the sidewall 222 of the bobbin case is vertically slabbed asat 242 substantially parallel to the chord along which the portion 240is cut away to define a shoulder 243 engageable with the step 218 formedin the top cover plate aperture 217 for restraining rotation of thebobbin case. The bobbin case sidewall 222 adjacent to the shoulder 243is formed with a vertical slot 244 through which bobbin thread passes tothe needle aperture 30 in the work supporting plate.

The bobbin case sidewall 222 and the projecting flange 225 are also cutaway as at 245 along a chord substantially parallel to the crosspiece212 when the bobbin case is positioned on the rotary hook.

Referring to FIGS. 7 and 12 which illustrate the under side of thebobbin case 40, a shallow recess 250 is formed in the bottom surface 221of the bobbin case. The recess 250 is partly circular in shape with achord 251 preferably formed substantially parallel to the cut awayportion 245 of the bobbin case sidewall. The recess 250 is preferablyformed slightly deeper than the largest diameter of thread which may behandled by the sewing machine and thus the recess serves to provideclearance for movement of the thread between portions of the bobbin case40 and the annular land 210 on the rotary hook. FIG. 6 includes in dotand dashed lines a representation of the position of the annular land210 relatively to the bobbin case 40 when the bobbin case is in place onthe rotary hook. In FIG. 7, the cross hatched area 210 in dicates thatportion of the annular land 210 which engages the bottom surface 221 ofthe bobbin case.

Referring to FIGS. 2, 3, 6, and 11 the frusto-conical outer surface ofthe bobbin case sidewall 222 is formed near the rim and parallel to theflange 226 with a thread supporting shelf 260 which extends from theslabbed portion 242 adjacent to the path of reciprocation of the needle57 approximately 180 about the rim of the bobbin case sidewall 222.

Operation With the bobbin case 40 in place on the rotary hook 20 and abobbin 41 wound with thread B in place in the bobbin case cavity 223,the rotary hook may be set in motion by closing a toggle switchcontrolling the.

motor 16. .As mentioned heretofore, in the embodiment illustrated in thedrawings the rotary book 20 will preferably be rotated at asubstantially constant velocity and in counterclockwise direction asviewed in FIGS. 4, 5,8A, 9A and 10A. The bobbin thread B will not beinfluenced by the rotating beaks 205 since the bobbin case slot 244 1through which the bobbin thread is directed to the needle aperture 30 issituated above the level of the bobbin case flange 226 which rests uponthe rotating beaks 205.

In preparation for sewing, the needle 57 must carry a needle thread Npreferably directed from a spool (not shown.) on the spool pin 62through the needle thread tension device 63, then to a take up eyelet ofthe take up mechanism 58, and finally through thread guides 101 and theeye of the needle. Upon insertion of a work fabric beneath the presserand feeding feet 135, 176, respectively the machine is in readiness tosew.

FIG. 2 illustrates the position of the needle and loop taker partsduring work penetration of the needle 57 as influenced either bymanually turning the balance wheel pulley 51 or by operator influence ofa speed control unit 85 for the motor 52. During each work penetration,the needle 57 will move through a range of positions in which the needlethread N carried thereby will be positioned for possible seizure by abeak 205 of the rotary hook. Although the particular range of needlepositions during which needle thread loop seizure by the hook beak ispossible may vary depending upon many specific factors such as theparticular kinematics of the needle reciproeating mechanism, the type ofneedle, for instance whether scarfed or not, and the condition and typeof needle thread and work fabrics being used, for any given conditions,the particular range is identifiable.

Any of the hook beaks 205 traversing the path of reciprocation of theneedle 57 while the needle occupies the thread loop presenting range ofpositions may seize the presented needle thread loop and carry theseized thread loop into a stored position on the bobbin case 40 asillustrated in FIGS. 3, 4, 6 and 7. FIGS. 8, 8A, 9 and 9A illustrate themanner in which any one of the hook beaks carries the needle thread loopinto the stored position on the bobbin case. When seized by any of thehook beaks 205, one limb Ns of the needle thread loop will extend fromthat beak to the needle eye and the other limb Nw will extend from thatbeak to the needle aperture 30. Since both thread limbs Ns and Nw extendalong chords spanning the circular path of the hook beaks 205, seizureof the needle thread loop by any other hook beak will be obviated. Onceseized by any one of the hook beaks 205, that limb Nw of the needlethread loop which extends directly to the needle aperture 30 and to thestitches in the work fabric is carried upwardly through the spaceprovided by the slabbed portion 240 on the bobbin case to the level ofthe shelf 260 on the bobbin case as illustrated in FIG. 8. That limb ofthe seized needle thread loop Ns which extends to the eye of the needleand thence to the needle thread supply is carried through the spaceprovided by the slabbed portion 240 and across the underside 221 of thebobbin case.

FIGS. 9 and 9A illustrate the position of parts and of the threads asthe hook beak 205 carries the needle thread loop on to the bobbin case40. It will be noted that the thread limb Nw is deposited on the shelf260 and the thread limb Ns is carried into the space between the annularland 210 on the rotary hook and the recess 250 in the undersnrface ofthe bobbin case which extends beyond the annular land 210 on that sidefrom which the thread limb N3 is introduced. FIGS. 9 and 9A alsoillustrate that both thread limbs Ns and Nw are turned about the needle57 as the thread limbs are drawn out by the hook beak 205. The fractionimposed by this turning about the needle coupled with the action of thebobbin case in spreading the thread loop by raising the limb Nw abovethe level of the hook beak and lowering the limb Ns below the level ofthe hook beak, draws the needle thread loop from the hook beak 205. Asillustrated in FIG. 9A the needle thread loop is about to be drawn fromthe hook beak and as illustrated in FIGS. 3, 4 and 6, the needle threadloop has been drawn from the hook beak and on to the cut away portion245 of the bobbin case sidewall out of the path of the hook beaks 205.

When the needle thread loop is drawn from the hook beak 205 into thestored position on the bobbin case as illustrated in FIGS. 3, 4 and 6,passage of the thread limb Ns beneath the bobbin case is blocked by thatportion 210' of the annular land 210 on the rotary hook which, asillustrated in FIG. 7, engages the underside 221 of the bobbin casebeyond the chord 251 of the shallow recess 250 therein.

Once deposited on the bobbin case the thread loop is stored in the sensethat further influence by any of the hook beaks is obviated. Thereafterthe thread loop is removable from the bobbin case only in response tofurther movements of the needle and take up mechanisms and completelyindependently of hook rotation. The raising of the needle eye togetherwith application of tension to the needle thread by operation of theneedle thread take up 58 will cause the limb Ns of needle thread whichis in the recess 250 beneath the bobbin case to exert a slight upwardforce on the bobbin case. Moreover, the upward lead of the thread limbNs to the raised needle eye will carry the thread across the bevel 241of the bobbin case as well as across the inclination of the slabbedportion 245 of the bobbin case. The combined effect of the upward forceapplied to the bobbin case together with the camming action of thebobbin case surfaces 241 and 245 will cause the needle thread limb Ns topass between the bottom surface 221 of the bobbin case and the annularland 210 of the rotary hook boss 206, as indicated by the alternateposition marked NsI in FIG. 10A. The needle thread loop is thus freed topass upwardly about the frusto-conical outer surface of the bobbin casesidewall 222 and upwardly out of the shelf 260 thereon to be drawn overthe upper flange 230 of the bobbin 41 between the bobbin and the leafspring 42 and thence through the needle aperture 30 and into the workfabric. The direction in which the needle thread loop is drawn from thestored position on the bobbin case is upwardly away from the rotary hookbeaks and the manipulation of the needle thread loop thus occurscompletely about the bobbin 41 within the bobbin case so that alockstitch thread concatenation is obtained. It will be appreciated thatas the needle thread loop is drawn upwardly from stored position on thebobbin case, the needle thread loop will be detained momentarily firstby the bowed extremity 216 of the spring 215, then by the leaf spring42, and finally by the rotation restraining shoulders 218, 243 on thecover plate 25 and bobbin case 40, respectively. The needle thread loopis thus controlled during the entire take up action while the stitch isbeing set so that the needle thread loop is prevented from accidentallyassuming a position in the path of any of the hook beaks 205.

While the above described needle and loop taker thus cooperate in theformation of stitches in the absence of any predetermined timed relationtherebetween, and the ratio of the rates of stitch forming motion ofneedle and loop taker may be varied during operation, it may benecessary to limit the maximum Speed ratio of needle to loop takermotion in order that perfect stitching may be attained with certainty.

One such limit of the maximum speed ratio is imposed by the necessityfor at least one beak 205 to traverse the path of needle reciprocationwithin each interval during which the needle occupies the range ofpositions described above in which needle loop seizure is possible, If,for example, each interval of possible needle loop seizure correspondsto 30 of rotation of the needle drive shaft 50, and only one beak 205 isused, the maximum ratio of needle reciprocation to rotary hook rotationof 1 to 12 ought not to be exceeded if needle loop seizure is to beattained with certainty. The use of a plurality of hook beaks permitsthe maximum speed ratio to be increased. For instance, in the aboveexample if four hook beaks 205 are employed this ratio limit becomes 1to 3, and with six such beaks 205 the ratio limit becomes 1 to 2 whichis most common in conventional lockstitch forming mechamsms.

While from the standpoint of needle loop seizure there is no theoreticallimit to the number of hook beaks which may be used and, therefore, fromthe loop seizure standpoint no theoretical limit as to the maximum speedratio, it will also be appreciated that an ascertainable increment ofturning movement of the loop taker is required in order to position theseized needle thread loop in stored relation on the bobbin case. Sincethe stored needle thread loop must thereafter be drawn from the bobbincase by the needle and take up mechanisms before the succeeding stitchconcatenation can take place, during which an additional increment ofturning movement of the loop taker will occur, these considerations ofthread manipulations will impose a practical limit to the maximum speedratio attainable regardless of the number of beaks employed.

Although the rotary hook is preferably rotated at a constant speed, itwill be appreciated that the rotary hook speed may be made variable,provided only that the maximum ratio of speed limits above described arenot exceeded. It is an important facet of this invention that shouldvariation of both loop taker and needle reciprocation rates be providedfor, synchronism or predetermined correlation as between these ratesneed not be observed.

It will be understood that the loop taker 20 comprises only threerelatively simple basic parts; the hook body 201, 202 and 203 is simplya cup-shaped member with a planar bearing face which may be readilyturned, cast, or mounded; the bobbin case 40 which also lends itselfreadily to manufacture by a moulding; and the top cover plate 25 whichis simply an apertured sheet metal element. Since the bobbin case flange226 simply rests upon the face of the rotary hook 20 and is notjournalled in a raceway into which the thread can become lodged, jammingof the hook, which has been a particularly irking problem with certainknown loop takers, is impossible with the present hook construction. Theraised boss 206 within the cup-shaped rotary hook is necessary only whenthe hook is to be driven in untimed relation with the needle. If aprecise timed relation is established, as is conventional, so thatstorage of the thread loop on the bobbin case becomes unnecessary theboss 206 may be dispensed with.

Having thus set forth the nature of this invention, what I claim hereinis:

1. A loop taker for lockstitch sewing machines having an endwisereciprocatory thread carrying needle, said loop taker including anannular member, at least one radially extending needle loop seizing beakformed on said annular member, means supporting said loop taker forturning movement in said sewing machine about a central axis, saidannular member formed on one face with a planar bearing surfaceperpendicular to said central axis, a bobbin case formed with a bearingflange engaging said planar bearing surface on said annular member,bobbin case retaining means supported independently of said loop takeron said sewing machine, andsaid bobbin case retaining means formed withbobbin case abutting surfaces providing the sole constraint for saidbobbin case radially, axially and angularly relatively to said planarbearing surface on said loop taker.

2. A loop taker as set forth in claim 1 in which said bobbin caseretaining means constrains said bobbin case bearing flange in engagementwith only a portion of said annular bearing surface on said annularmember.

3. A loop taker as set forth in claim 1 in which said loop seizing beakis defined on the annular member by a notch formed radially of saidannular member and said needle loop seizing beak extends substantiallyto the plane of said planar bearing surface on said annular member.

References Cited UNITED STATES PATENTS 1,996,290 4/ 1935 Gunther 112-228X 2,544,227 3/1951 Hohmann 112-184 2,966,130 12/1960 Johnson 112-184FOREIGN PATENTS 537,634 2/ 1957 Canada.

HERBERT F. ROSS, Primary Examiner.

